Given a string s which represents an expression, evaluate this expression and return its value.
The integer division should truncate toward zero.
Example 1:
Input: s = "3+2*2"
Output: 7
Example 2:
Input: s = " 3/2 "
Output: 1
Example 3:
Input: s = " 3+5 / 2 "
Output: 5
Constraints:
1 <= s.length <= 3 * 10^5sconsists of integers and operators ('+', '-', '*', '/') separated by some number of spaces.- s represents a valid expression.
- All the integers in the expression are non-negative integers in the range
[0, 2^31 - 1]. - The answer is guaranteed to fit in a 32-bit integer.